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I spend a lot of times on other areas of stackexchange, but this looked to be the best place to ask the following question. Feel free to let me know if it isn't.

I'm going to layout exactly what I'm trying to do, though I'll be asking my questions in multiple parts. I just wanted you guys to have all the pertinent information when considering your answer.

I'm trying to make a pet gravesite marker out of concrete. Here is what it will roughly look like.

Model

It'll be about 2' long. It's going to be located in the mountains. Elevation is 4070', record low temps were -24deg, avg lowest yearly temp is 18deg. Lots of rain and tons of snow. Average highs are in the low 90's.

I'm going to need to make it to last. I work at a metal shop, so I plan to cut metal inserts, such as: a silhouette, name, birth/death date, and maybe a decorative border. I plan to stain it black so that it matches the horse's show colors of black and silver. I also wouldn't mind some light flakes of some kind to make the black pop a little. I haven't worked that out yet.

I'll build a form with the face open and level. I'll pour in the concrete and then set the inserts into the face while it cures. I'll use a hand sander and stick to vibrate the form and remove air bubbles and inclusions. I'll sand the face and metal inserts flush to accommodate any shrinking that occurred and make sure the face is perfectly flush. I'll buff the metal till it's bright and scratch free. After curing, I'll see if the inserts are easily removable. If they are, I'll remove them before staining. Lastly, I'll seal it against tarnish and the elements.

I should end up with a headstone shaped approximately like the one pictured and it'll be black (possibly with small metallic flakes) with silver looking inserts.

My first question on the project is what combination of concrete, stain, and sealant will handle the weather conditions I mentioned above. I had planned to use Portland cement from home depot. I heard it was extremely hard and durable. I found another page where they were making headstones for the graves of American pioneers and they said to use morter mix. I'm not well versed in concrete and don't know if the two are mutually exclusive.

I do know that Portland cement doesn't set up to a light color and I don't think the black stain will look good if I'm not applying it to a lighter color. Again, I'll also have to seal it against all that nasty weather.

So what do you guys recommend I use for this project. I figured I'd use Portland cement and add some colorant to get it to a lighter color to stain and polish it black. Then seal it with something durable. I know there are additives to concrete to make it more elastic or something, but I really don't know what they are or what they do. Thanks for helping me out here. Let me know if I need to clarify anything.

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    Typically, headstones are cut from granite. – Ben Welborn Jul 20 '16 at 20:22
  • The ones that last the best certainly are (from my time in looking around old graveyards and observing the condition of the stones from similar ages but different materials.) Plenty of good showy black granite out there that would have enough sparkles to call the silver to mind. – Ecnerwal Jul 20 '16 at 20:28
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Concrete pigments are available. But for what I think you are wanting, you would start by grinding/sanding the block smooth, then painting it (black) with an epoxy base coat, then sprinkling it with decorative metallic/colored flakes (the loose fines are cleaned off), and then a clear epoxy top coat is layed over it.

Here's a youtube video for this procedure (on a garage floor): https://www.youtube.com/watch?v=YjEI1P9vtGg.

Extra steps to ensure a longer life for the concrete?

I would probably use either waterproof additive or waterproof concrete (with premixed additive). And I would definitely opt for the UV resistant epoxy.

I might also consider using a silane or siloxane (impregnating) based grout sealer for pre-sealing the concrete (which might not be worth the cost- I'm not sure; since you are covering it with epoxy anyway). But to estimate, lets say a quart costs $20, and it will basically cover 100 square ft, (or 10 headstones)... I might be tempted to do it because it might help if the concrete starts to crack or chip after a while. Good (silane or siloxane) grout sealers tend to hold up for 1 to 3 decades, so for the price, I might do it... but honestly, I don't know if it would help.

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You're a metal worker? How about stainless?

This DiY Headstone suggests high strength mortar mix.

You should use colorant to achieve your final color instead of attempting to stain it afterwards, which would only be skin deep.


However, this is why you use granite:

enter image description here

I'd suggest Uba Tuba for its flakes:

enter image description here

Truly though, what I'd recommend, is having a real stone cut for you. They're not as expensive as I would've thought. Even a somewhat fancy one should be under a grand. But it doesn't really matter what we think... what does The Boss want?

This:

enter image description here

Or this:

enter image description here

Food for thought, regarding the fact that you're a metalsmith, if your only tool is a hammer...

If it needs to last, then it needs to be made out of granite.

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